Can I Paint On Buttercream

I am making a cake for a friend and I have an idea in my head of what I want it to look like but I would need to paint it. My friend does not really like fondant so I would rather just do it with buttercream. If I get the buttercream really smooth and let it crust over will I be able to paint it?

Thanks guys, you have been very helpful. I think that I am just going to paint on fondant this time but I will play around with painting on buttercream really soon. I'm not sure that I will ever be good enough to paint WITH buttercream. That is amazing. Thanks for the threads, I looked them up but I couldn't find any. This is my first time posting a question on here and I am so appreciative of the help. I am sure I will be using it again in the future.